Systems for vending beverages such as cola, juice, beer, etc. is roughly classified into two types.
The first type is a system in which used containers are not recovered. In general, this is called as one-way system. According to this system, for instance, beverages are filled in cans at a factory, being transported to an automatic vending machine and consumed by the consumer. The can containing the beverage is not recovered and is thereafter discarded by him.
The second type is a system in which used containers are recovered and which can be called as two-way system. In this system, for instance, beverages are bottled at a factory, being transported to an automatic vending machine and consumed by the consumer. The bottles containing the beverages are recovered for reuse.
The one-way system is generally convenient and has been widely employed as a preferable system. Recently, however, there is a strong voice demanding that two-way system should be adopted in view of the economical efficiency of reusing bottles or the effective use of an automobile transporting such beverages.
An important problem in the two-way system is what kind of inspection and washing should be conducted in order to obtain containers for re-use.
Hitherto, the following procedure has been adopted, for example, i.e. recovered containers are visually inspected by a human and the containers considered uncleanable are removed and only the good containers are washed.
Such human inspection is an operation which is simple but requires him to be under a great amount of tension. Therefore, its mechanization has been demanded.
In contrast, the following inspection has been suggested, i.e. an inspection by which the beverage residue in the recovered container is withdrawn and then the residue is analyzed by means of an analyzer. However, since the inspection using such analyzer takes much time and is costly, this is not efficient.